Without being bound by theory, it is believed that the anti-fungal mechanism of action of pyrithione-containing antifungals involves the inhibition of aconitase and other mitochondrial iron-sulfur proteins. The mechanism of inhibition is believed to involve the formation of copper pyrithione within the cell by either association with exogenous or endogenous copper and transchelation according to the Irving-Williams series. The copper pyrithione can then traverse the mitochondrial membrane and interact with iron-sulfur proteins such as aconitase resulting in alteration of the iron-sulfur active site and resultant inhibition of activity.
In the present invention it was found that the ZPT sensitivity increased with a CUP2 deletion strain that is defective in protection from high copper levels. From this and other observations, it is appreciated that copper is augmenting the effect of ZPT induced growth inhibition, but the mechanism was unknown.
Through the present invention, including the results of ZPT sensitivity of the Saccharomyces deletion library strains, it is found that mitochondrial iron sulfur protein maturation is a key target of ZPT. This is confirmed by the present invention's demonstration that, in minimal medium, ZPT inhibits growth by inhibition of glutamate and lysine synthesis, which require the activity of the mitochondrial iron-sulfur protein aconitase. Moreover, culturing of cells in the presence of ZPT has led to aconitase inhibition. The present invention has extended the understanding of the ZPT mechanism of action to identification of a key target enzyme.